The present invention relates generally to detector systems. More particularly, the present invention relates to a detector system equipped to correct defective pixel values therein.
A solid state detector contains a plurality of photodetector elements. For example, a radiographic x-ray detector can include several million photodetector elements to correspondingly provide an image having several million pixels. Such a detector typically comprises a scintillating layer in contact with an array of photodiodes arranged in rows and columns. Each photodiode converts impinging light into an electrical charge or signal proportional thereto, and in turn, each electrical signal is processed and converted into a digital value. The resulting array of digital valves comprise the image data for the image to be displayed.
In the course of manufacturing such a detector, a certain number of photodetector elements will invariably be defective. Because pixel size is chosen such that objects of interest in the image will be greater than the size of an individual pixel, a perfect detector is not required for imaging. However, if defective or bad pixels are aggregated in sizeable clusters, the loss of relevant information may be considerable. Alternatively, since defective pixel values would either be independent of the impinging light, because the corresponding detector locations are not photonically and/or electrically responsive, or be dependent of the impinging light but in manner statistically different from its neighboring pixels, if defective pixels are left unaltered in the displayed image, they would distract from the visualization of the rest of the image.
Presently, there are known methods for identifying and correcting defective pixel values prior to displaying the image. These correction methods replace each defective pixel value with an interpolation of its neighboring pixel values. Such correction methods, however, are quite susceptible to creating image artifacts, such as breaks in guide wires, because the correction relies only on the defective pixel""s surrounding pixels, i.e., the eight pixels surrounding the defective pixel, and uses static correction schemes. Instead, by basing the correction upon temporal image content, selective neighboring pixels of each defective pixel can be utilized to avoid image artifacts, such as breaks in guide wires.
Thus, there is a need for a correction method that provides a more accurate correction of defective pixels. There is a further need for an apparatus and method configured to utilize image feature information and temporal information to perform defective pixel correction.
One embodiment of the invention relates to a method for correcting a defective pixel in a current image produced by a detector. The current image includes an array of pixels and each element in the array of pixels has a corresponding pixel value. The method includes determining a correction value of the defective pixel in the current image based on a gradient. The gradient is comprised in part using the current image and an image produced by the detector selected from a group including at least one prior image and at least one future image.
Another embodiment of the invention relates to a system for correcting a defective pixel in a current image produced by a detector. The current image includes an array of pixels and each element in the array of pixels has a corresponding pixel value. The system includes a processor coupled to the detector. The processor is configured to determine a correction value of the defective pixel in the current image based on a gradient. The gradient is comprised in part using the current image and another image produced by the detector selected from a group including at least one prior image and at least one future image.
Still another embodiment of the invention relates to a system for correcting a defective pixel. The system includes means for producing a current image and an another image selected from a group including a prior image and a future image. The current image includes an array of pixels and each element in the array of pixels has a corresponding pixel value. The system further includes means for determining a correction value of the defective pixel in the current image. The determination of the correction value is based on a gradient, the gradient comprised in part using the current image and the another image.